POS0461 DISRUPTED HIPPOCAMPAL NEUROGENESIS MEDIATED BY IL-6 AND IL-18 INDUCE NEUROPSYCHIATRIC CHANGES IN MURINE LUPUS
Authors: D. Nikolopoulos, T. Manolakou, A. Polissidis, A. Filia, Y. Koutmani, D. Boumpas
Journal: Annals of the Rheumatic Diseases (2022)

Background Systemic lupus erythematosus (SLE) frequently affects the nervous system (NPSLE), however, its pathogenesis is only partly understood. We have previously characterized the behavioral phenotype of the NZΒ/W-F1 lupus-prone mouse which recapitulates the NPSLE phenotype exhibiting hippocampal-linked behavior including depressive-like disorder, anxiety and cognitive impairment both at early and late stages of the disease characterized by a profound hippocampal inflammatory response1,2. Defective hippocampal neural stem cell (hNSC) response is associated with cognitive dysfunction, depression and anxiety, all of which represent common neuropsychiatric features of both human and murine SLE. Objectives To further investigate the hippocampal neurogenesis in lupus mice and determine its involvement in disease pathogenesis. Methods All experiments were performed in female NZW/NZB F1 and C57BL/6 (WT) mice at the age of 3 months (pre-nephritic) and 6 months (nephritic stage) (n=5-8/condition/experiment). Neurogenesis was assessed in sagittal sections of hippocampus by immunohistochemical staining (DCX, Sox2, GFAP, Iba1) and morphological criteria. RNA-sequencing was performed in hippocampal tissue followed by pathway and enrichment analysis. Apoptosis (cleaved-caspase 3) and immune cell infiltration (CD11b, CD45, Ly6G, Ly6C, MHC-II, CD4, CD8, B220, Iba1, CD80, CD86, Argianse-1, iNOS) were assessed by flow-cytometry. Cytokines levels were measured by Legendplex. Ex vivo assays were performed in adult hippocampal neural stem cells extracted by 2-month-old female WT mice. Results We identified a profound disruption (~2-fold) of hippocampal neurogenesis (decreased DCX+ cells) both at 3 ad 6 month-old lupus mice together with decreased differentiated cells in both time-points, suggesting that lupus mice exhibit impaired neuronal differentiation. Although the number of the neuronal precursors radial glial-like cells (RGLs) was normal at pre-nephritic stage, lupus mice express increased number of both activated RGLs (Sox2+/GFAP+) and proliferating neuronal progenitors (Sox2+ cells) indicating enhanced self-renewal ability of neural precursors and augmented proliferation. Levels of cleaved-caspase 3 were elevated in lupus hippocampus supporting increased hippocampal apoptosis. Transcriptomic analysis of hippocampal tissue revealed a profound inflammatory response in lupus mice. Flow-cytometry analyses showed a pronounced immune cell trafficking in lupus hippocampus with a myeloid predominant response –involving predominantly the microglia- both at early and late stages of the disease. Multiplex assays revealed elevated levels of IL-6 and IL-18 in lupus hippocampus. Ex vivo exposure of adult hNSCs to IL-6 or IL-18 promoted cell proliferation and induced apoptosis. Conclusion The NZB/W-F1 mouse model of SLE exhibits defective neurogenesis due to increased apoptosis, and decreased differentiation of neuronal progenitors. Inflammation in lupus hippocampus results in elevated levels of IL-6 and IL-18 with both cytokines negatively affecting the hNSCs response. IL-6 and IL-18 may induce behavioral changes in NZB/W-F1 lupus mediated by altered neurogenesis and may represent therapeutic targets in NPSLE. References [1]Nikolopoulos, D., et al. “THU0223 THE NEUROPSYCHIATRIC PHENOTYPE OF NZB/W LUPUS-PRONE MOUSE MODEL AT PRE-NEPHRITIC AND NEPHRITIC STAGES OF THE DISEASE: MURINE MODEL RECAPITULATES HUMAN DISEASE.” (2020): 334-335. http://dx.doi.org/10.1136/annrheumdis-2020-eular.1807 [2]Nikolopoulos D. et al. “OP0040 HIPPOCAMPAL IMMUNE CELL TRAFFICKING AND A MYELOID PREDOMINANT INFLAMMATORY RESPONSE WITH ENHANCED ANTIGEN PRESENTATION AND DECREASED LEVELS OF NEUROTRANSMITTERS UNDERLY THE NEUROPSYCHIATRIC PHENOTYPE OF THE NZW/NZB MURINE LUPUS MODEL.” (2021): 2021. http://dx.doi.org/10.1136/annrheumdis-2021-eular.3972 Acknowledgements This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No 742390) Disclosure of Interests None declared.